Mitsubishi Electric QJ71LP21 Reference Manual page 4

[Design Precautions]
• When performing control operations to a PLC (modifying data) in operation by connecting GX
Developer to the CPU module or connecting personal computers to the intelligent functional
modules, configure an interlocking circuit in a sequence program so that the safety of the overall
system is maintained. Also, before performing other control operations (program modifications
and operating status modifications (status control)) on the PLC in operation, be sure to read the
manual thoroughly and confirm the safety. Especially if the above mentioned control operations
are performed from an external device to a remote PLC, problems arising on the PLC side may
not be dealt with immediately due to abnormal data communication. Thus, in addition to
configuring an interlocking circuit in a sequence program, determine how the system should
handle data communication errors between the PLC CPU and external devices.
• Always reset the CPU module after changing the parameters for the CPU module or the remote
I/O module. If this is not done, data from before the change could cause malfunctioning.
• Do not bundle the control wires and communication cables with the main circuit or power wires,
or install them close to each other. They should be installed at least 100 mm (3.94 in.) away
from each other. Failure to do so may generate noise that may cause malfunctions.
[Installation Precautions]
• Use the PLC in the operating environment that meets the general specifications described in the
user's manual for the CPU module used. Using the PLC in any other operating environments
may cause electric shocks, fires or malfunctions, or may damage or degrade the product.
• With holding down the module installation lever on the lower part of the module, securely insert
the module fastening latch in the installation hole on the base unit to install the module using the
module installation hole as a supporting point. If the module is not installed properly, it may
cause the module to malfunction, fail or fall off.
Secure the module with screws especially when it is used in an environment where constant
vibrations may occur.
Be sure to tighten the screws using the specified torque. If the screws are loose, it may cause
the module to short-circuit, malfunction or fall off. If the screws are tightened excessively, it may
damage the screws and cause the module to short-circuit, malfunction or fall off.
• Before mounting or dismounting the module, make sure to shut off all phases of the external
power supply. Failure to do so may damage the product.
For remote I/O stations of function version D or later, online module change can be performed.
However, the modules which can be replaced online are limited, and replacement procedures
are determined for each module. For details, refer to the section of online module replacement
in this manual.
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